Bacterial hemoglobin receptor gene

ABSTRACT

The present invention relates to a novel bacterial hemoglobin receptor protein and genes that encode such a protein. The invention is directed toward the isolation, characterization, diagnostic and therapeutic use of a bacterial hemoglobin receptor protein, nucleic acid encoding such a protein, recombinant expression constructs comprising such nucleic acids and cells transformed therewith, and antibodies and epitopes of such hemoglobin receptor proteins. The invention relates particularly to hemoglobin receptor proteins and genes encoding such proteins from Neisseria species, especially N. meningitidis. Methods for the diagnostic and therapeutic use of the proteins, epitopes, antibodies and nucleic acids of the invention are also provided, including the use of the proteins, epitopes, antibodies and nucleic acids of the invention for the production of vaccines effective in providing immunization of a human against infection by pathogenic bacteria of Neisseria species.

This invention was made with government support under National Institute of Health grants R01 AI32493 and R01 AI22933. The government has certain rights to this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to hemoglobin receptor genes and the proteins encoded therefrom of certain bacterial species, particularly species of Neisseria bacteria. More particularly, this invention relates to hemoglobin receptor genes, polypeptides and peptides useful for preparing vaccines and antibodies against Neisseria, and methods and means for producing such peptides and polypeptides in vitro. Also provided are diagnostic and therapeutic methods and reagents useful in detecting and treating Neisseria infection and methods for developing novel and effective anti-Neisseria agents.

2. Background of the Invention

The Neisseria comprise a genus of bacteria that includes two gram-negative species of pyogenic cocci pathogenic for humans: Neisseria meningitidis and Neisseria gonorrhoeae. N. meningitidis is a major cause of bacterial meningitis in humans, especially children. The disease characteristically proceeds from asymptomatic carriage of the bacterium in the nasopharynx to invasion of the bloodstream and cerebrospinal fluid in susceptible individuals.

Neisseria meningitidis is one of the leading causes of bacterial meningitis in children and healthy adults in the world. The severity of the disease is epitomized by the ability of meningococci to cause the death of previously healthy individuals in less than 24 hours. N. meningitidis has a polysaccharide capsule whose diversity of component antigenic polysaccharide molecules has resulted in the classification of ten different serogroups. Of these, group A strains are the classic epidemic strains; group B and C are generally endemic strains, but C occasionally causes an epidemic outbreak. All known group A strains have the same protein antigens on their outer membranes, while group B strains have a dozen serotypes or groupings based on the presence of principal outer membrane protein antigens (as opposed to polysaccharides).

Survival of a pathogen such as N. meningitidis in a host depends on its ability to overcome a battery of host defense mechanisms. One nonspecific host defense mechanism against microbial intruders is to limit the availability of iron in tissues (Weinberg, 1984, Physiological. Rev. 64: 65-102), because iron is a necessary nutrient for most microbial pathogens. The vast majority of iron in the human adult is located intracellularly in the form of haemoglobin (76%) or ferritin (23%). The remainder can be found extracellularly bound to host iron-binding proteins such as transferrin and lactoferrin (Otto et al., 1992, Crit. Rev. Microbiol. 18: 217-233).

Pathogenic bacteria have adapted to this iron-limiting environment by developing highly specific and effective iron assimilation systems. A large number of these bacteria secrete siderophores, small, non-protein iron chelators which, due to their extremely high affinity for iron (III), scavenge trace mounts of iron(III) from the environment and shuttle the iron back to the bacterial cell (Baggs and Neilands, 1987, Microbiol. Rev. 51: 509-518; Braun and Hantke, 1991, in Winkelmann (ed.), Handbook of Microbial Iron Chelates, CRC Press: Boca Raton, Fla., pp. 107-138.).

Alternatively, some bacterial pathogens, like Neisseriae species (Archilbald and DeVoe, 1979, FEMS Microbiol. Lett. 6: 159-162; Mickelson et al., 1982, Infect. Immun. 35: 915-920; Dyer et al., 1987, Infect. Immun. 55: 2171-2175), Haemophilus influenzae (Coulton and Pang, 1983, Curr. Microbiol. 9: 93-98; Schryvers, 1988, Mol. Microbiol. 2: 467-472; Jarosik et al., 1994, Infect. Immun. 62: 2470-2477), Vibrio cholerae (Stoebner and Payne, 1988, Infect. Immun. 56: 2891-2895; Henderson and Payne, 1994, J. Bacteriol. 176: 3269-3277), Yersiniae (Stojiljkovic and Hantke, 1992, EMBO J. 11: 4359-4367) and Actinobacillus pleuropneumoniae (Gerlach et al., 1992, Infect. Immun. 60: 3253-3261) have evolved more sophisticated mechanisms to sequester iron from the host. These pathogens can directly bind host's iron-binding proteins such as lactoferrin, transferrin, and haem-containing compounds, and use them as sole sources of iron.

The importance of iron in the virulence of N. meningitidis was demonstrated by in vivo studies using mice as the animal model system (Calver et al., 1976, Can. J. Microbiol. 22: 832-838; Holbien et al., 1981, Infect. Immun. 34: 120-125). Specific iron-regulated outer membrane receptors have been shown to be involved in the binding and the utilization of lactoferrin- and transferrin-iron in Neisseriae (Schryvers and Morris, 1988, Infect. Immun. 56: 1144-1149 and Mol. Microbiol. 2: 281-288; Legrain et al., 1993, Gene 130: 81-90; Pettersson et al., 1993, Infect. Immun. 61: 4724-4733 and 1994, J. Bacteriol. 176: 1764-1766). These receptors share significant amino acid similarity and, most probably, also the mechanism of iron internalization, with receptors for siderophores and vitamin B12 of other Gram-negative bacteria (Cornelissen et al., 1993, J. Bacteriol. 174: 5788-5797). In contrast, the mechanism by which Neisseriae utilize hemoglobin- and hemin-iron as well as the components involved have so far not been described.

Recently, several proteins with hemoglobin-binding and/or hemin-binding activities have been identified in total membranes of iron-limited N. meningitidis and N. gonorrhoeae.

Lee and Hill, 1992, J. gen. Microbiol. 138: 2647-2656 disclose the specific hemoglobin binding by isolated outer membranes of N. meningitidis.

Martek and Lee, 1994, Infect. Immun. 62: 700-703 disclosed that acquisition of heme iron by N. meningitidis does not involve meningococcal transferrin-binding proteins.

Lee, 1994, Microbiol. 140: 1473-1480 describes the biochemical isolation and characterization of hemin binding proteins from N. meningitidis.

The precise role of these proteins in hemin and/or hemoglobin utilization remains unclear at present, although these proteins are likely to be components of a hemin-utilization system in N. meningitidis.

The dependence on host iron stores for Neisseria growth is a potentially useful route towards the development of novel and effective therapeutic intervention strategies. Historically, infections of both N. meningitidis and N. gonorrhoeae were treated chemoprophylactically with sulfonamide drugs. However, with the development of sulfonamide-resistant strains came the necessity of using alternative modes of therapy such as antibiotic treatment. More recently, the drug treatment of choice includes the administration of high grade penicillin. However, the success of antimicrobial treatment is decreased if therapy is not initiated early after infection.

Gonococcal infection has also been treated with penicillin, ampicillin, or amoxicillin, tetracycline hydrochloride, and spectinomycin. Unfortunately, because the incidence of infections due to penicillinase-producing bacteria has increased, several new, more expensive β-lactam antibiotics have been used in treatment. Despite the fact that existing antibiotics have decreased the serious consequences of gonorrhea, their use has not lowered the incidence of the infection in the general population.

Prevention of meningococcal disease has been attempted by chemoprophylaxis and immunoprophylaxis. At present, rifampin and minocycline are used, but only for humans in close contact with an infected person as this treatment has a number of disadvantages. The only commercially available vaccine against meningococcal meningitis has as its major component the bacterial polysaccharide capsule. In adults this vaccine protects against serogroups A, C, Y and W135. It is not effective against serogroup B, and is ineffective in children against serogroup C. Thus far, immunoprophylatic preventive treatment has not been available for N. gonorrhoeae.

Thus, what is needed are better preventative therapies for meningococcal meningitis and D. gonorrhoeae including more effective, longer lasting vaccines which protect across all of the serogroups of N. meningitidis and all the serotypes of N. gonorrhoeae. In addition, better methods are need to treat meningococcal and gonococcal infection.

SUMMARY OF THE INVENTION

The present invention relates to the cloning, expression and functional characterization of a bacterial hemoglobin receptor protein. Specifically, the invention relates to such a hemoglobin receptor protein from Neisseria species, in particular Neisseria meningitidis. The invention comprises a nucleic acid having a nucleotide sequence encoding a novel bacterial hemoglobin receptor protein. Also provided by this invention is the deduced amino acid sequence of the cognate hemoglobin receptor protein of this bacterial gene.

The invention provides nucleic acids, nucleic acid hybridization probes, recombinant expression constructs capable of expressing the hemoglobin receptor protein of the invention in cultures of transformed cells, preferably bacterial cells, and such cultures of transformed bacterial cells that express the hemoglobin receptor protein of the invention. The invention also provides gene knockout vectors for inactivating the hemoglobin receptor protein gene in cells, particularly cells of Neisseria species, via, for example, homologous recombination and other mechanisms, and cultures of such hemoglobin receptor protein null mutant cells.

The invention also provides homogeneous preparations of the bacterial hemoglobin receptor proteins of the invention, as well as antibodies against and epitopes of the hemoglobin receptor protein. Methods for characterizing this receptor protein and methods for using the protein in the development of agents having pharmacological uses related to this receptor, particularly bactericidal and bacteriostatic uses, are also provided by the invention.

In other embodiments of this invention are provided diagnostic methods and reagents encompassing the use of the anti-Neisseria hemoglobin receptor protein antibodies of the invention. Still further embodiments provided herein include therapeutic methods and reagents encompassing the use of the anti-Neisseria hemoglobin receptor protein antibodies of the invention. Even more embodiments include diagnostic methods and reagents encompassing the use of the Neisseria hemoglobin receptor protein-encoding nucleic acids of the invention, as sensitive probes for the presence of Neisseria infection using nucleic acid hybridization techniques and/or in vitro amplification methodologies. Yet additional embodiments of the invention include therapeutic methods and reagents encompassing the use of the Neisseria hemoglobin receptor protein-encoding nucleic acids of the invention, comprising recombinant expression constructs engineered to produce antisense transcripts of the Neisseria hemoglobin receptor gene and fragments thereof, as well as recombinant knockout vectors of the invention. The invention also provides the Neisseria hemoglobin receptor protein and epitopes thereof as components of vaccines for the development of non-disease associated immunity to pathological infection with bacteria of Neisseria species.

In a first aspect, the invention provides a nucleic acid having a nucleotide sequence encoding a bacterial hemoglobin receptor protein gene. In a preferred embodiment, the bacterial hemoglobin receptor protein gene is isolated from bacteria of Neisseria species. In a particularly preferred embodiment, the hemoglobin receptor protein gene is isolated from Neisseria meningitidis. In a particular example of this embodiment, the nucleic acid comprises a 3.3 kilobase (kb) BamHI/HindlII fragment of N. meningitidis genomic DNA. In this embodiment, the nucleotide sequence comprises an open reading frame of 2376 nucleotides of N. meningitidis genomic DNA encoding 792 amino acids comprising the hemoglobin receptor gene. In this embodiment of the invention, the nucleotide sequence of the N. meningitidis hemoglobin receptor gene is the sequence depicted in FIG. 2A-2H (SEQ ID No:1). It will be understood that the N. meningitidis gene as disclosed herein is defined, insofar as is necessary, by the amino acid sequence of the protein encoded therein, said amino acid sequence being represented in FIGS. 2A-2H (SEQ. ID No.:2). Thus, it will be understood that the particular nucleotide sequence depicted in FIGS. 2A-2H (SEQ. ID. No.:1) is but one of a number of equivalent nucleotide sequences that encode the hemoglobin receptor protein, due to the degeneracy of the genetic code, and that all such alternative, equivalent nucleotide sequences are hereby explicitly encompassed within the disclosed nucleotide sequences of the invention. Also included herein are any mutant or allelic variations of this nucleotide sequence, either naturally occurring or the product of in vitro chemical or genetic modification. Each such variant will be understood to have essentially the same nucleotide sequence as the nucleotide sequence of the corresponding N. meningitidis hemoglobin receptor protein disclosed herein.

The invention also provides a bacterial hemoglobin receptor protein. In a preferred embodiment, the bacterial hemoglobin receptor protein is isolated from bacteria of Neisseria species. In a particularly preferred embodiment, the hemoglobin receptor protein is isolated from Neisseria meningitidis. In a particular example of this embodiment, the protein comprises an amino acid sequence of 792 amino acids. In this embodiment of the invention, the amino acid sequence of the N. meningitidis hemoglobin receptor protein is the sequence depicted in FIGS. 2A-2H (SEQ ID No:2). Also encompassed within the scope of this invention are related bacterial hemoglobin receptor proteins, particularly such proteins isolated from Neisseria species, having essentially the same arnino acid sequence and substantially the same biological properties as the hemoglobin receptor protein encoded by the N. meningitidis nucleotide sequence described herein.

In another aspect, the invention provides a homogeneous preparation of a 85.5 kiloDalton (kD) bacterial hemoglobin receptor protein or derivative thereof, said size being understood to be the size of the protein before any post-translational modifications thereof. Also provided is a 90 kD embodiment of the receptor as determined by sodium dodecyl sulfate/ polyacrylamide gel electrophoresis under reducing conditions. In a preferred embodiment, the bacterial hemoglobin receptor protein is isolated from bacteria of Neisseria species. In a particularly preferred embodiment, the hemoglobin receptor protein is isolated from Neisseria meningitidis. In this embodiment, the amino acid sequence of the bacterial hemoglobin receptor protein or derivative thereof preferably is the amino acid sequence of the N. meningitidis hemoglobin receptor protein shown in FIGS. 2A-2H (SEQ ID No:2).

This invention provides nucleotide probes derived from the nucleotide sequence herein provided. The invention includes probes isolated from either complementary DNA (cDNA) copies of bacterial messenger RNA (mRNA) or bacterial genomic DNA (gDNA), as well as probes made synthetically with the sequence information derived therefrom. The invention specifically includes but is not limited to oligonucleotide, nick-translated, random primed, or in vitro amplified probes made using cDNA or genomic clone embodying the invention, and oligonucleotide and other synthetic probes synthesized chemically using the nucleotide sequence information of cDNA or genomic clone embodiments of the invention.

It is a further object of this invention to provide such nucleic acid hybridization probes to detect the presence of bacteria of Neisseria species, particularly N. meningitidis, in a biological sample in the diagnosis of a Neisseria infection in a human. Such a biological sample preferably includes blood, urine, semen, mucus, cerebrospinal fluid, peritoneal fluid and ascites fluids, as well as cell scrapings from the epithelium of the mouth, urethrae, anus and rectum, and other organs.

The present invention also includes peptides encoded by the nucleotide sequences comprising the nucleic acid embodiments of the invention. The invention includes either naturally occurring or synthetic peptides which may be used as antigens for the production of hemoglobin receptor protein-specific antibodies. The invention also comprises such antibodies, preferably monoclonal antibodies, and cells and cultures of cells producing such antibodies.

Thus, the invention also provides antibodies against and epitopes of bacterial hemoglobin receptor proteins of the invention. It is an object of the present invention to provide antibodies that are immunologically reactive to the bacterial hemoglobin receptor proteins of the invention. It is a particular object to provide monoclonal antibodies against these bacterial hemoglobin receptor proteins. In a preferred embodiment, antibodies provided are raised against bacterial hemoglobin receptor protein isolated from bacteria of Neisseria species. In a particularly preferred embodiment, such antibodies are specific for the hemoglobin receptor protein isolated from Neisseria meningitidis.

Hybridoma cell lines producing such antibodies are also objects of the invention. It is envisioned that such hybridoma cell lines may be produced as the result of fusion between a non-immunoglobulin producing mouse myeloma cell line and spleen cells derived from a mouse immunized with purified hemoglobin receptor protein or a cell expressing antigens or epitopes of a bacterial hemoglobin receptor protein of the invention. The present invention also provides hybridoma cell lines that produce such antibodies, and can be injected into a living mouse to provide an ascites fluid from the mouse that is comprised of such antibodies. In a preferred embodiment, antibodies provided are raised against bacterial hemoglobin receptor protein isolated from bacteria of Neisseria species. In a particularly preferred embodiment, such antibodies are specific for the hemoglobin receptor protein isolated from Neisseria meningitidis.

It is a further object of the invention to provide immunologically-active epitopes of the bacterial hemoglobin receptor proteins of the invention. Chimeric antibodies immunologically reactive against the bacterial hemoglobin receptor proteins of the invention are also within the scope of this invention. In a preferred embodiment, antibodies and epitopes provided are raised against or derived from bacterial hemoglobin receptor protein isolated from bacteria of Neisseria species. In a particularly preferred embodiment, such antibodies and epitopes are specific for the hemoglobin receptor protein isolated from Neisseria meningitidis.

The present invention provides recombinant expression constructs comprising a nucleic acid encoding a bacterial hemoglobin receptor protein wherein the construct is capable of expressing the encoded hemoglobin receptor protein in cultures of cells transformed with the construct. Preferred embodiments of such constructs comprise the N. meningitidis hemoglobin receptor gene depicted in FIGS. 2A-2H (SEQ ID No.: 1), such constructs being capable of expressing the bacterial hemoglobin receptor protein encoded therein in cells transformed with the construct.

The invention also provides cultures of cells, preferably bacterial cells, having been transformed with the recombinant expression constructs of the invention, such cultures being capable of and in fact expressing the bacterial hemoglobin receptor protein encoded in the transforming construct.

The present invention also includes within its scope protein preparations of prokaryotic cell membranes containing the bacterial hemoglobin receptor protein of the invention, derived from cultures of prokaryotic cells transformed with the recombinant expression constructs of the invention.

The invention also provides diagnostic reagents and methods for using such reagents for detecting the existence of an infection in a human, with bacteria of a Neisseria species. In preferred embodiments, such diagnostic reagents comprise antibodies that are immunologically reactive with a bacterial hemoglobin receptor protein. In a preferred embodiment, such antibodies are raised against a bacterial hemoglobin receptor protein isolated from bacteria of Neisseria species. In a particularly preferred embodiment, such antibodies are specific for the hemoglobin receptor protein isolated from Neisseria meningitidis.

In yet another embodiment of this aspect of the invention are provided diagnostic reagents and methods for using such reagents wherein said reagents are nucleic acid hybridization probes comprising a bacterial hemoglobin receptor gene. In a preferred embodiment, the bacterial hemoglobin receptor protein gene is isolated from bacteria of Neisseria species. In a particularly preferred embodiment, the hemoglobin receptor protein gene is isolated from Neisseria meningitidis. In particular examples of this embodiment of the invention, the nucleic acid probes comprise a specifically-hybridizing fragment of a 3.3 kilobase (kb) BamHI/HindIII fragment of N. meningitidis genomic DNA. In this embodiment, the nucleotide sequence comprises all or a specifically-hybridizing fragment of an open reading frame of 2376 nucleotides of N. meningitidis genomic DNA encoding 792 amino acids comprising the hemoglobin receptor gene. In this embodiment of the invention, the nucleotide sequence of the N. meningitidis hemoglobin receptor gene is the sequence depicted in FIGS. 2A-2H (SEQ ID No: 1). It will be understood that the term "specifically-hybridizing" when used to describe a fragment of a nucleic acid encoding a bacterial hemoglobin receptor gene is intended to mean that nucleic acid hybridization of such a fragment is stable under high stringency conditions of hybridization and washing as the term "high stringency" would be understood by those having skill in the molecular biological arts.

Also provided by the invention are therapeutic agents and methods for using such agents for treating the an infection in a human with bacteria of a Neisseria species. In preferred embodiments, such agents comprise antibodies that are immunologically reactive with a bacterial hemoglobin receptor protein. In a preferred embodiment, such antibodies are raised against a bacterial hemoglobin receptor protein isolated from bacteria of Neisseria species. In a particularly preferred embodiment, such antibodies are specific for the hemoglobin receptor protein isolated from Neisseria meningitidis. Therapeutic agents provided in this aspect of the invention comprise such antibodies in a pharmaceutically-acceptable carrier, along with appropriate adjuvants and the like. In additional embodiments, such antibodies are covalently conjugated to a bactericidal or bacteriostatic agent effective against bacteria of Neisseria species, preferably N. meningitidis.

In yet another embodiment of this aspect of the invention are provided therapeutic reagents and methods for using such reagents wherein said reagents comprise recombinant expression constructs of the invention, or a homologue thereof that expresses the nucleic acid encoding a hemoglobin receptor in an antisense orientation. In a preferred embodiment, the bacterial hemoglobin receptor protein gene is isolated from bacteria of Neisseria species. In a particularly preferred embodiment, the hemoglobin receptor protein gene is isolated from Neisseria meningitidis. In particular examples of this embodiment of the invention, the nucleic acid probes comprise a specifically-hybridizing fragment of a 3.3 kilobase (kb) BamHI/HindIII fragment of N. meningitidis genomic DNA. In this embodiment, the nucleotide sequence comprises all or a specifically-hybridizing fragment of an open reading frame of 2376 nucleotides of N. meningitidis genomic DNA encoding 792 amino acids comprising the hemoglobin receptor gene.

The invention also provides a method for screening compounds for their ability to inhibit, facilitate or modulate the biochemical activity of a bacterial hemoglobin receptor protein of the invention, for use in the in vitro screening of novel agonist and antagonist compounds and novel bactericidal and bacteriostatic agents specific for the hemoglobin receptor protein. In preferred embodiments, cells transformed with a recombinant expression construct of the invention are contacted with such a compound, and the binding capacity of the compounds, as well as the effect of the compound on binding of other, known hemoglobin receptor agonists, such as hemoglobin and hemin, and antagonists is assayed. Additional preferred embodiments comprise quantitative analyses of such effects.

The present invention is also useful for the detection of bactericidal and/or bacteriostatic analogues, agonists or antagonists, recognized or unrecognized, of a bacterial hemoglobin receptor protein, preferably derived from bacteria of Neisseria species, most preferably isolated from N. meningitidis, wherein such compounds are either naturally occurring or embodied as a drug.

The invention also provides vaccines for immunizing a human against infection with pathogenic bacteria of Neisseria species, the vaccines comprising the hemoglobin binding proteins of the invention or antigenic fragments thereof. In a preferred embodiment, the vaccines of the invention comprise cells expressing a hemoglobin receptor binding protein of the invention, or an antigenic fragment thereof, preferably wherein said cells are attenuated varieties of cells adapted for growth in humans. Examples of such attenuated varieties of cells include attenuated strains of Salmonella typhi and Salmonella typhimurium.

Specific preferred embodiments of the present invention will become evident from the following more detailed description of certain preferred embodiments and the claims.

DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of the present invention, the various features thereof, as well as the invention itself may be more fully understood from the following description, when read together with the accompanying drawings in which:

FIG. 1 is a schematic drawing of the restriction enzyme digestion map of a N. meningitidis cosmid clone and subclones thereof derived as described in Example 2.

FIG. 2A-2H illustrates the nucleotide (SEQ ID No. :1) and deduced amino acid (SEQ ID No.:2) sequences of the N. meningitidis hemoglobin receptor protein encoded in a 3.3 kb BamHI/HindIII DNA fragment.

FIG. 3 presents a photograph of a stained SDS/10 % PAGE electrophoresis gel showing the results of in vitro expression of the N. meningitidis hemoglobin receptor gene product as an approximately 90 kilodalton protein, and β-lactamase protein having a molecular weight of about 30.0 kilodaltons used as a molecular weight marker.

FIGS. 4A-4C presents an amino acid sequence comparison between portions of the N. meningitidis transferrin receptor Tbpl (SEQ ID Nos. 3 & 4), the N. meningitidis lactoferrin receptor LbpA (SEQ ID Nos.: 5 & 6), and N. meningitidis hemoglobin receptor HmbR (SEQ ID No. :2).

FIG. 5 illustrates Southern hybridization analysis of chromosomal DNA from N. meningitidis 8013 and the MC8013hmbR mutant using a BamHI-SalI fragment of the hmb gene as probe labeled using a DIG nonradioactive DNA labelling and detection kit (Boehringer Mannheim Biochemicals, Indianapolis, Ind.). Lane 1 contains DNA from N. meningitidis strain MC8013, digested with ClaI; lane 2 is MC8031hmbR DNA digested with ClaI; lane 3, is MC8013 DNA digested with BamHI and SalI; and lane 4 is MC8013hmbR DNA digested with BamHI and SalI.

FIG. 6 is a graph describing the course of infection using N. meningitidis wild type (MC8013) and hmbR mutant strains in an in vivo rat infant infection model. Each strain was injected intraperitoneally (2×10⁶ CFU into three infant inbred Lewis rats. The results represent the average of two similarly-performed experiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term "bacterial hemoglobin receptor" as used herein refers to bacterial proteins comprising the outer membrane of Gram negative bacteria, which specifically mediate transit of hemoglobin-derived hemin, as well as heroin from other sources, through the outer membrane of such bacteria and into the periplasmic space. The bacterial hemoglobin receptor proteins of the invention are characterized by, first, an amino acid sequence that is essentially the sequence depicted in FIGS. 2A-2H (SEQ ID No.:2). The bacterial hemoglobin receptor proteins of the invention are further characterized by having substantially the same biological activity as a protein having the amino acid sequence depicted in FIGS. 2A-2H (SEQ ID No. :2). This definition is intended to encompass naturally-occurring variants and mutant proteins, as well as genetically engineered variants made by man.

Cloned, isolated and purified nucleic acid provided by the present invention may encode a bacterial hemoglobin receptor protein of any Neisseria species of origin, including, most preferably, Neisseria meningitidis and Neisseria gonorhoeae species.

The nucleic acid hybridization probes provided by the invention comprise DNA or RNA having all or a specifically-hybridizing fragment of the nucleotide sequence of the hemoglobin receptor protein as depicted in FIGS. 2A-2H (SEQ ID No. :1), or any portion thereof effective in nucleic acid hybridization. Mixtures of such nucleic acid hybridization probes are also within the scope of this embodiment of the invention. Nucleic acid probes as provided herein are useful for detecting the presence of a bacteria, inter alia, in a human as the result of an infection, in contaminated biological samples and specimens, in foodstuffs and water supplies, or in any substance that may come in to contact with the human. Specific hybridization will be understood to mean that the nucleic acid probes of the invention are capable of forming stable, specific hybridization to bacterially-derived DNA or RNA under conditions of high stringency, as the term "high stringency" would be understood by those with skill in the art (see, for example, Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. and Hames and Higgins, eds., 1985, Nucleic Acid Hybridization, IRL Press, Oxford, U.K.). Hybridization will be understood to be accomplished using well-established techniques, including but not limited to Southern blot hybridization, Northern blot hybridization, in situ hybridization and Southern hybridization to polymerase chain reaction product DNAs. The invention will thus be understood to provide oligonucleotides, specifically, pairs of oligonucleotides, for use as primers in support of in vitro amplification of bacterial hemoglobin receptor genes and mRNA transcripts.

The production of proteins such as bacterial hemoglobin receptor proteins from cloned genes by genetic engineering means is well known in this art. The discussion which follows is accordingly intended as an overview of this field, and is not intended to reflect the full state of the art. It will be understood from the following discussion that the hemoglobin receptor protein genes of this invention are particularly advantageous, since expression of such proteins by bacteria, including non-Neisseria species of bacteria, can complement certain auxotrophic mutants of said transformed bacteria otherwise unable to subsist absent supplementation of the growth media with iron (III).

DNA encoding a bacterial hemoglobin receptor protein can be prepared in view of the instant disclosure, by chemical synthesis, by screening reverse transcripts of mRNA from appropriate cells, by screening genomic libraries from appropriate cells, or by combinations of these procedures, as illustrated below. Screening of mRNA or genomic DNA may be carried out with oligonucleotide probes generated from the nucleic acid sequence information from the bacterial hemoglobin receptor protein disclosed herein. Probes may be labeled with a detectable group such as a fluorescent group, a radioactive atom or a chemiluminescent group in accordance with know procedures and used in conventional hybridization assays, as described in greater detail in the Examples below. In the alternative, bacterial hemoglobin receptor protein-encoding nucleic acids may be obtained by use of the polymerase chain reaction (PCR) procedure, using appropriate pairs of PCR oligonucleotide primers corresponding to nucleic acid sequence information derived from a bacterial hemoglobin receptor protein as provided herein. See U.S. Pat. Nos. 4,683,195 to Mullis et al. and 4,683,202 to Mullis. In another alternative, such bacterial hemoglobin receptor protein-encoding nucleic acids may be isolated from auxotrophic cells transformed with a bacterial hemoglobin receptor protein gene, thereby relieved of the nutritional requirement for uncomplexed iron (III).

Any bacterial hemoglobin receptor protein of the invention may be synthesized in host cells transformed with a recombinant expression construct comprising a nucleic acid encoding the bacterial hemoglobin receptor protein. Such recombinant expression constructs can also be comprised of a vector that is a replicable DNA construct. Vectors are used herein either to amplify DNA encoding a bacterial hemoglobin receptor protein and/or to express DNA encoding a bacterial hemoglobin receptor protein. For the purposes of this invention, a recombinant expression construct is a replicable DNA construct in which a nucleic acid encoding a bacterial hemoglobin receptor protein is operably linked to suitable control sequences capable of effecting the expression of the bacterial hemoglobin receptor protein in a suitable host cell.

The need for such control sequences will vary depending upon the host cell selected and the transformation method chosen. Generally, bacterial control sequences include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding sites (the Shine-Delgarno sequence), and sequences which control the termination of transcription and translation. Amplification vectors do not require expression control domains. All that is needed is the ability to replicate in a host, usually conferred by an origin of replication, and a selection gene to facilitate recognition of transformants. See, Sambrook et al., 1989, ibid.

Vectors useful for practicing the present invention include plasmids and virus-derived constructs, including phage and particularly bacteriophage, and integratable DNA fragments (i.e., fragments integratable into the host genome by homologous recombination). The vector replicates and functions independently of the host genome, or may, in some instances, integrate into the genome itself. Suitable vectors will contain replicon and control sequences which are derived from species compatible with the intended expression host. A preferred vector is pLAFR2 (see Riboli et al., 1991, Microb. Pathogen. 10: 393-403).

Transformed host cells are cells which have been transformed or transfected with recombinant expression constructs made using recombinant DNA techniques and comprising nucleic acid encoding a bacterial hemoglobin receptor protein. Preferred host cells are cells of Neisseria species, particularly N. meningitidis, Salmonella typhi and Salmonella typhimurium, and Escherichia coli auxotrophic mutant cells (hemA aroB). Transformed host cells may express the bacterial hemoglobin receptor protein, but host cells transformed for purposes of cloning or amplifying nucleic acid hybridization probe DNA need not express the receptor protein. When expressed, the bacterial hemoglobin receptor protein of the invention will typically be located in the host cell outer membrane. See, Sambrook et al., ibid.

Cultures of bacterial cells, particularly cells of Neisseria species, and certain E. coli mutants, are a desirable host for recombinant bacterial hemoglobin receptor protein synthesis. In principal, any bacterial cell auxotrophic for uncomplexed iron (III) is useful for selectively growing bacterial hemoglobin receptor protein-transformed cells. However, for this purpose, well-characterized auxotrophs, such as E. coli hemA aroB routants are preferred.

The invention provides homogeneous compositions of a bacterial hemoglobin receptor protein produced by transformed cells as provided herein. Each such homogeneous composition is intended to be comprised of a bacterial hemoglobin receptor protein that comprises at least 90% of the protein in such a homogenous composition. The invention also provides membrane preparations from cells expressing a bacterial hemoglobin receptor protein as the result of transformation with a recombinant expression construct of the invention, as described herein.

Bacterial hemoglobin receptor proteins, peptide fragments thereof and membranes derived from cells expressing such proteins in accordance with the present invention may be used for the production of vaccines effective against bacterial infections in a human, with pathogenic microorganisms expressing such bacterial hemoglobin receptor proteins. Such vaccines preferably would be effective in raising an immunological response against bacteria of Neisseria species, most preferably N. meningitidis and N. gonorhoeae. Preparation of vaccines which contain polypeptide sequences as active ingredients is well understood in the art. Typically, such vaccines are prepared as injectables, either as liquid solutions or suspensions. However, solid forms suitable for solution in, or suspension in, liquid prior to injection may also be prepared. The preparation may also be emulsified. The active immunogenic ingredient is often mixed with excipients which are pharmaceutically acceptable and compatible with the active ingredient. Suitable excipients are, for example, water, saline, dextrose, glycerol, ethanol, or the like and combinations thereof. In addition, if desired, the vaccine may contain minor amounts of auxiliary substances such as wetting or emulsifying agents, pH buffering agents, or adjuvants which enhance the effectiveness of the vaccine. The vaccines are conventionally administered parenterally, by injection, for example, either subcutaneously or intramuscularly. Additional formulations which are suitable for other modes of administration include suppositories and, in some cases, oral formulations. For suppositories, traditional binders and carriers may include, for example, polyalkalene glycols or triglycerides; such suppositories may be formed from mixtures containing the active ingredient in the range of 0.5% to 10%, preferably 1 to 2%. Oral formulations include such normally employed excipients as, for example, pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate and the like. These compositions take the form of solutions, suspensions, tablets, pills, capsules, sustained release formulations or powders and contain 10% to 95% of active ingredient, preferably 25 to 70%.

The polypeptide may be formulated into the vaccine as neutral or salt forms. Pharmaceutically acceptable salts include the acid additional salts (formed with the free amino groups of the peptide) and which are formed with inorganic acids such as, for example, hydrochloric or phosphoric acids, or such organic acids as acetic, oxalic, tartaric, mandelic, and the like. Salts formed with the free carboxyl groups may also be derived from inorganic bases such as, for example, sodium, potassium, ammonium, calcium, or ferric hydroxides, and such organic bases as isopropylamine, trimethylamine, 2-ethylamino ethanol, histidine, procaine, and the like.

In another embodiment, such vaccines are provided wherein the bacterial hemoglobin receptor proteins or peptide fragments thereof are present in the intact cell membranes of cells expressing such proteins in accordance with the present invention. In preferred embodiments, cells useful in these embodiments include attenuated varieties of cells adapted to growth in humans. Preferred examples of such attenuated cells include attenutated varieties of Salmonella typhi and Salmonella typhimurium. It will be understood that these embodiments of the vaccines of the invention encompass so-called "live" attenuated cell preparations as well as heat- or chemically-inactivated cell preparations.

The vaccines of the invention are administered in a manner compatible with the dosage formulation, and in such amount as will be therapeutically effective and immunogenic. The quantity to be administered depends on the subject to be treated, capacity of the subject's immune system to synthesize antibodies, and the degree of protection desired. Precise amounts of active ingredient required to be administered depend on the judgment of the practitioner and are peculiar to each individual. However, suitable dosage ranges are of the order of several hundred micrograms active ingredient per individual. Suitable regimes for initial administration and booster shots are also variable, but are typified by an initial administration followed in one or two week intervals by a subsequent injection or other administration.

The recombinant expression constructs of the present invention are useful in molecular biology to transform bacterial cells which do not ordinarily express a hemoglobin receptor protein to thereafter express this receptor. Such cells are useful, inter alia, as intermediates for making cell membrane preparations useful for receptor binding activity assays, vaccine production, and the like, and in certain embodiments may themselves be used, inter alia, as vaccines or components of vaccines, as described above. The recombinant expression constructs of the present invention thus provide a method for screening potentially useful bactericidal and bacteriostatic drugs at advantageously lower cost than conventional screening protocols. While not completely eliminating the need for ultimate in vivo activity and toxicology assays, the constructs and cultures of the invention provide an important first screening step for the vast number of potentially useful bactericidal and bacteriostatic drugs synthesized, discovered or extracted from natural sources each year. In addition, such bactericidal or bacteriostatic drugs would be selected to utilize a nutritional pathway associated with infectious virulence in these types of bacteria, as disclosed in more detail below, thus selectively targeting bacteria associated with the development of serious infections in vivo.

Also, the invention provides both functional bacterial hemoglobin receptor proteins, membranes comprising such proteins, cells expressing such proteins, and the amino acid sequences of such proteins. This invention thereby provides sufficient structural and functional activity information to enable rational drug design of novel therapeutically-active antibacterial drugs using currently-available techniques (see Walters, "Computer-Assisted Modeling of Drugs", in Klegerman & Groves, eds., 1993, Pharmaceutical Biotechnology, Interpharm Press: Buffalo Grove, Ill., pp. 165-174).

Nucleic acids and oligonucleotides of the present invention are useful as diagnostic tools for detecting the existence of a bacterial infection in a human, caused by a hemoglobin receptor protein-expressing pathological organism of Neisseria species. Such diagnostic reagents comprise nucleic acid hybridization probes of the invention and encompass paired oligonucleotide PCR primers, as described above. Methods provided by the invention include blot hybridization, in situ hybridization and in vitro amplification techniques for detecting the presence of pathogenic bacteria in a biological sample. Appropriate biological samples advantageously screened using the methods described herein include plasma, serum, lymph, cerebrospinal fluid, seminal fluid, mucosal tissue samples, biopsy samples, and other potential sites of bacterial infection. It is also envisioned that the methods of the invention may be used to screen water, foodstuffs, pharmaceuticals, and other potential sources of infection.

The invention also provides antibodies that are immunologically reactive to a bacterial hemoglobin receptor protein or epitopes thereof provided by the invention. The antibodies provided by the invention may be raised, using methods well known in the art, in animals by inoculation with cells that express a bacterial hemoglobin receptor protein or epitopes thereof, cell membranes from such cells, whether crude membrane preparations or membranes purified using methods well known in the art, or purified preparations of proteins, including fusion proteins, particularly fusion proteins comprising epitopes of a bacterial hemoglobin receptor protein of the invention fused to heterologous proteins and expressed using genetic engineering means in bacterial, yeast or eukaryotic cells, said proteins being isolated from such cells to varying degrees of homogeneity using conventional biochemical means. Synthetic peptides made using established synthetic means in vitro and optionally conjugated with heterologous sequences of amino acids, are also encompassed in these methods to produce the antibodies of the invention. Animals that are used for such inoculations include individuals from species comprising cows, sheep, pigs, mice, rats, rabbits, hamsters, goats and primates. Preferred animals for inoculation are rodents (including mice, rats, hamsters) and rabbits. The most preferred animal is the mouse.

Cells that can be used for such inoculations, or for any of the other means used in the invention, include any cell that naturally expresses a bacterial hemoglobin receptor protein as provided by the invention, or any cell or cell line that expresses a bacterial hemoglobin receptor protein of the invention, or any epitope thereof, as a result of molecular or genetic engineering, or that has been treated to increase the expression of an endogenous or heterologous bacterial hemoglobin receptor protein by physical, biochemical or genetic means. Preferred cells are E. coli auxotrophic mutant hemA aroB cells transformed with a recombinant expression construct of the invention and grown in media supplemented with heroin or hemoglobin as the sole iron (III) source, and cells of Neisseria species.

The present invention also provides monoclonal antibodies that are immunologically reactive with an epitope of a bacterial hemoglobin receptor protein of the invention, or fragment thereof, present on the surface of such cells, preferably E. coli cells. Such antibodies are made using methods and techniques well known to those of skill in the art. Monoclonal antibodies provided by the present invention are produced by hybridoma cell lines, that are also provided by the invention and that are made by methods well known in the art (see Harlow and Lane, 1988, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. ).

Hybridoma cell lines are made by fusing individual cells of a myeloma cell line with spleen cells derived from animals immunized with a homogeneous preparation of a bacterial hemoglobin receptor protein, membranes comprised thereof, cells expressing such protein, or epitopes of a bacterial hemoglobin receptor protein, used per se or comprising a heterologous or fusion protein construct, as described above. The myeloma cell lines used in the invention include lines derived from myelomas of mice, rats, hamsters, primates and humans. Preferred myeloma cell lines are from mouse, and the most preferred mouse myeloma cell line is P3X63-Ag8.653. Preferred animals from whom spleens are obtained after immunization are rats, mice and hamsters, preferably mice, most preferably Balb/c mice. Spleen cells and myeloma cells are fused using a number of methods well known in the art, including but not limited to incubation with inactivated Sendai virus and incubation in the presence of polyethylene glycol (PEG). The most preferred method for cell fusion is incubation in the presence of a solution of 45% (w/v) PEG-1450. Monoclonal antibodies produced by hybridoran cell lines can be harvested from cell culture supernatant fluids from in vitro cell growth; alternatively, hybridoma cells can be injected subcutaneously and/or into the peritoneal cavity of an animal, most preferably a mouse, and the monoclonal antibodies obtained from blood and/or ascites fluid.

Monoclonal antibodies provided by the present invention are also produced by recombinant genetic methods well known to those of skill in the art, and the present invention encompasses antibodies made by such methods that are immunologically reactive with an epitope of a bacterial hemoglobin receptor protein of the invention. The present invention also encompasses fragments, including but not limited to F(ab) and F(ab)'₂ fragments, of such antibody. Fragments are produced by any number of methods, including but not limited to proteolytic cleavage, chemical synthesis or preparation of such fragments by means of genetic engineering technology. The present invention also encompasses single-chain antibodies that are immunologically reactive with an epitope of a bacterial hemoglobin receptor protein, made by methods known to those of skill in the art.

The antibodies and fragments used herein can be labeled preferably with radioactive labels, by a variety of techniques. For example, the biologically active molecules can be labeled with a radionucleotide via conjugation with the cyclic anhydride of diethylenetriamine penta-acetic acid (DPTA) or bromoacetyl aminobenzyl ethylamine diamine tetra-acidic acid (BABE). See Hnatowich et al. (1983, Science 220: 613-615) and Meares et al. (1984, Anal. Biochem. 142: 68-78, both references incorporated by reference) for further description of labeling techniques.

The present invention also encompasses an epitope of a bacterial hemoglobin receptor protein of the invention, comprised of sequences and/or a conformation of sequences present in the receptor molecule. This epitope may be naturally occurring, or may be the result of proteolytic cleavage of a receptor molecule and isolation of an epitope-containing peptide or may be obtained by synthesis of an epitope-containing peptide using methods well known to those skilled in the art. The present invention also encompasses epitope peptides produced as a result of genetic engineering technology and synthesized by genetically engineered prokaryotic or eukaryotic cells.

The invention also includes chimeric antibodies, comprised of light chain and heavy chain peptides immunologically reactive to a bacterial hemoglobin receptor protein-derived epitope. The chimeric antibodies embodied in the present invention include those that are derived from naturally occurring antibodies as well as chimeric antibodies made by means of genetic engineering technology well known to those of skill in the art.

Also provided by the present invention are diagnostic and therapeutic methods of detecting and treating an infection in a human, by pathogenic organisms expressing a bacterial hemoglobin receptor protein. Diagnostic reagents for use in such methods include the antibodies, most preferably monoclonal antibodies, of the invention. Such antibodies are used in conventional immunological techniques, including but not limited to enzyme-linked immunosorbent assay (ELISA), radioimmune assay (RIA), Western blot assay, immunological titration assays, immunological diffusion assays (such as the Ouchterlony assay), and others known to those of skill in the art. Also provided are epitopes derived from a bacterial hemoglobin receptor protein of the invention and immunologically cross-reactive to said antibodies, for use in any of the immunological techniques described herein.

Additional diagnostic assays include nucleic acid hybridization assays, using the nucleic acids of the invention or specifically-hybridizing fragments thereof, for sensitive detection of bacterial genomic DNA and/or mRNA. Such assays include various blot assays, such as Southern blots, Northern blots, dot blots, slot blots and the like, as well as in vitro amplification assays, such as the polymerase chain reaction assay (PCR), reverse transcriptase-polymerase chain reaction assay (RT-PCR), ligase chain reaction assay (LCR), and others known to those skilled in the art. Specific restriction endonuclease digestion of diagnostic fragments detected using any of the methods of the invention, analogous to restriction fragment linked polymorphism assays (RFLP) are also within the scope of this invention.

The invention also provides therapeutic methods and reagents for use in treating infections in a human, cause by a microorganism expressing a bacterial hemoglobin receptor protein of the invention, most preferably a bacteria of Neisseria species. Therapeutic reagents for use in such methods include the antibodies, most preferably monoclonal antibodies, of the invention, either per se or conjugated to bactericidal or bacteriostatic drugs or other antibiotic compounds effective against the infectious microorganism. In such embodiments, the antibodies of the invention comprise pharmaceutical compositions, additionally comprising appropriate pharmaceutically-acceptable carriers and adjuvants or other ancillary components where necessary. Suitable carriers are, for example, water, saline, dextrose, glycerol, ethanol, or the like and combinations thereof. In addition, if desired, the pharmaceutical formulation may contain minor amounts of auxiliary substances such as wetting or emulsifying agents, pH buffering agents, or other compounds which enhance the effectiveness of the antibody. In these embodiments, it will be understood that the therapeutic agents of the invention serve to target the infectious bacteria, either by immunologically "tagging" the bacteria with an antibody of the invention for recognition by cytotoxic cells of a human's immune system, or by specifically delivering an antimicrobial drug to the infectious microorganism via the bacterial hemoglobin receptor protein.

Additional therapeutic reagents include the nucleic acids of the invention or fragments thereof, specifically antisense embodiments of such nucleic acids. Such antisense nucleic acids may be used themselves or embodied in a recombinant expression construct specific for antisense expression, wherein said construct is genetically engineered to co-opt a portion of the genome of a bacterial virus, preferably a bacteriophage, infectious for the bacterial pathogen responsible for the infection. In these embodiments, introduction of the antisense nucleic acids of the invention into the bacterial cell inhibits, attenuated or abolishes expression of the bacterial hemoglobin receptor, thereby reducing the virulence of the bacterial infection and enabling more effective antibacterial interventions. In additional embodiments, bacteriophage are provided bearing "knockout" copies of a bacterial hemoglobin receptor gene, whereby the phage achieves genetic mutation of the endogenous hemoglobin receptor gene in the infectious bacteria via, for example, homologous recombination of the exogenous knockout copy of the bacterial hemoglobin receptor gene with the endogenous hemoglobin receptor gene in the infectious microorganism.

The Examples which follow are illustrative of specific embodiments of the invention, and various uses thereof. They set forth for explanatory purposes only, and are not to be taken as limiting the invention.

EXAMPLE 1 Plasmids, Bacteria, and Media

Plasmids and bacteria used herein are listed on Table 1. E. coli strains were routinely grown in Luria-Bertani (LB) broth supplemented with 5-aminolevulinic acid and 50 mg/L hemin chloride as necessary. N. meningitidis 8013 is a serogroup C clinical isolate (Nassif et al., 1993, Mol. Microbiol. 8: 719-725). The meningococci were routinely grown on GCB agar (Difco) supplemented as described by Kellogg et aI. (1963, J. Bacteriol 85: 1274-1279), and incubated at 37° C. under a 5% CO₂ atmosphere. Transformation of meningococci was performed as described by Nassif et al. (1992, Mol. Microbiol. 6: 591-597). When necessary, the following antibiotics were used with E. coli: rifampicin, 100 mg/L; tetracycline, 15 mg/L; kanamycin, 30 mg/L; chloramphenicol, 20 mg/L; carbenicillin, 100 mg/L. For Neisseriae, kanamycin at 100 mg/L was used when needed.

EXAMPLE 2 Auxotroph Complementation Cloning of a Hemoglobin Receptor Gene from Neisseria meningitidis

In order to identify N. meningitidis outer membrane receptor(s) involved in the uptake of hemin and/or hemoglobin iron, an auxotroph complementation cloning strategy was used, similar to the approach previously taken to identify the Y. enterocolitica and V. cholerae hemin

                  TABLE I                                                          ______________________________________                                         Bacterial Strains and Plasmids                                                             GENOTYPE                                                           ______________________________________                                         STRAIN                                                                         E. coli K12                                                                    EB53          hemA, aroB, rpoB                                                 KP1041        MC4100tonB::Km.sup.r                                             H1388         exbB::Tn10 Δlac pro                                        TSM348        endA, hsdR, pro, supF, pRK2013::Tn9                              IR754         EB53, tonB::Km.sup.r                                             IR736         EB53, exbB::Tn10                                                 DH5α    recA, gyrB                                                       N. meningitidis                                                                MC8013        clone 6, wild type                                               MChmbR        hmbR::aphA-3                                                     PLASMIDS                                                                       pSUSK         pA15 replicon, chloramphenicol.sup.r                             pHEM22        pLAR2, hemoglobin-utilizing cosmid                               pHEM44        pLAFR2, hemin-utilizing cosmid                                   pIRS508       6kb ClaI, pSUSK                                                  pIRS523       3kb BamHI/SalI, pUC19                                            pIRS525       1.2kb aphA-3, in NotI site of pIRS523                            pIRS527       4kb BamHI/ClaI, pBluescript                                      pIRS528       0.7kb NotI/BamHI, pBluescript                                    pIRS692       3.3kb BamHI/HindIII, SU(SK)                                      ______________________________________                                    

receptors (see Stojiljkovic and Hantke, 1992, EMBO J. 11: 4359-4367; Henderson and Payne, 1994, J. Bacteriol. 176: 3269-3277). This strategy is based on the fact that the outer membrane of Gram-negative bacteria is impermeable to heroin (McConville and Charles, 1979, J. Microbiol. 113: 165-168) and therefore E. coli porphyrin biosynthesis mutants cannot grow on exogenously supplied hemin. If provided with the N. meningitidis outer membrane hemin receptor gene, the E. coli porphyrin mutant would be able to use exogenously supplied hemin as its porphyrin source.

A cosmid bank of N. meningitidis 8013 clone 6 DNA was prepared using conventional cosmid cloning methodologies (Sambrook et al., 1989, ibid.). N. meningitidis bacterial DNA was partially digested by MboI, size fractionated on sucrose gradients and cloned into the BamHI site of the cosmid vector pLAFR2 (Riboli et al., 1991, Microb. Pathogen. 10: 393-403). This cosmid bank was mobilized into the E. coli hemA aroB Rif' recipient strain by triparental matings using a conjugal plasmid pRK2013::Tn9. The mating mixture was plated on selective plates containing hemin chloride (50 mg/L), 0.1 mM 2,2'-dypyridil and rifampicin (100 mg/L). Several clones growing on exogenously supplied hemin were isolated after an overnight incubation.

The hemin utilization phenotype of these transformants was tested by re-introduction of the cosmids into naive E. coli hemA aroB cells and by monitoring the growth on hemin-supplemented plates. The ability of E. coli strains to utilize heme or hemoglobin as the sole iron source was tested as previously described (Stojiljkovic and Hantke, 1992, ibid.). Cells were grown on LB agar supplemented with 50 μM deferoxamine mesylate (an iron chelating agent, obtained from Sigma Chemical Co., St. Louis, Mo.). Filter discs (1/4 inches, Schleichner & Schuell, Inc., Keene, N.H.) impregnated with the test compounds (20 μL of 5 mg/ml stock solutions unless otherwise stated) were placed on these plates. After overnight growth at 37° C. with 5% CO₂, zones of growth around the discs were monitored. The iron-bound proteins tested in this assay (all obtained from Sigma Chemical Co.) were hemoglobin from human, baboon, bovine and mouse sources, bovine heroin, human lactoferrin (90% iron saturated), and human transferrin (90% iron saturated, obtained from Boehringer Mannheim Biochemicals, Indianapolis, Ind.). A total of six heroin utilization positive cosraids were obtained using this protocol. Results using such assays are shown in Table II.

                                      TABLE II                                     __________________________________________________________________________     STRAIN   φ-TYPE                                                                               HEMIN IRON                                                                             PORPHYRIN                                                                             Hb IRON                                      __________________________________________________________________________     N. meningitidis                                                                MC8013   wild type +++     N.T.   +++                                          MChmbR   Hb.sup.R mutant                                                                          +++     N.T.   -                                            E. coli                                                                        EB53     iron utilization                                                                         -       -      -                                            EB53 (pIRS508)                                                                          tonB.sup.+, exbB.sup.+, hmbR.sup.+                                                       +++     +++    +                                            IR754(pIRS508)                                                                          tonB.sup.-, exbB.sup.+, hmbR.sup.+                                                       -       -      -                                            IR736(pIRS508)                                                                          tonB.sup.+, exbB.sup.-, hmbR.sup.+                                                       -       -      -                                            __________________________________________________________________________      N.T. -- not tested. Use of hemin/hemoglobin as a porphyrin source was          tested by scoring for growth of strains around hemin (5 mg/mL) or              hemoglobin (for E. coli, 10 mg/mL; for N. meningitidis, 5 mg/mL) discs on      LB plates. The use of the hemin/hemoglobin as an iron source was tested        similarly except NBD plates supplemented with 50 μL of 5 g/L                deltaaminolevulinic acid were used (GCB plates supplemented with the 50        μM Desferal in the case of N. meningitidis).                                --: indicates no growth; +: less than 100 mm of growth zone around the         disc; +++: ±15 mm of growth zone around the disc.                     

EXAMPLE 3 Restriction Enzyme Digestion Mapping of Hemin Utilization Positive Cosmids

Cosmid DNA from six hemin-utilization positive cosmids obtained as described in Example 2 were digested with ClaI, and the resulting fragments were cloned into ClaI-digested pSU(SK) vector (obtained from Stratagene, LaJolla, Calif.). One subclone, containing a 6 kb Clal fragment from cosmid cos22 (the resultant plasmid was designated pIRS508), was determined to allow utilization of hemin and hemoglobin by E. coli hemA aroB assayed as described in Example 2. Another such clone, containing an 11 kb ClaI fragment from cos44 was also determined to allow heroin utilization in these auxotrophic mutant cells. Restriction analysis and Southern hybridization indicated that the DNA fragments originating from cos22 and cos44 are unrelated.

The deduced restriction enzyme digestion map of cosmid clone pIRS508 is shown in FIG. 1. Plasmid pIRS508 enabled E. coli hemA aroB to use both heroin and bovine hemoglobin as iron sources although growth on hemoglobin was somewhat weaker than on hemin (Table 2). Further subcloning localized the hemin/hemoglobin utilization locus to the BamHI/HindIII fragment of the insert. In addition to sequences encoding the hemoglobin receptor gene (designated hmbR), sequences for a Neisseria insertion element (IS1106) and a portion of a Neisseria small repetitive element (IR1) are also represented in the Figure.

EXAMPLE 4 Nucleotide Sequence Analysis of a Cosmid Clone Encoding a Neisseria Hemoglobin Receptor Gene

The nucleotide sequence of the 3.3 kb BamHI-HindIII DNA fragment carrying the hmbR gene and its promoter region was determined using the dideoxy chain termination method using a Sequenase 2.0 kit (obtained from U.S. Biochemicals, Cleveland, Ohio) and analyzed using a BioRad electrophoresis system, an AutoRead kit (obtained from Pharmacia, Uppsala, Sweden) and an ALF-370 automatic sequenator (Pharmacia). Plasmid subclones for sequencing were produced by a nested deletion approach using Erase-a-Base kit (obtained from Promega Biotech, Madison, Wis.) using different restriction sites in the hmbR gene. The nucleotide and predicted amino acid sequences of the hmbR gene are shown in FIG. 2A-2H.

An open reading frame (ORF) encoding the N. meningitidis hemoglobin receptor protein begins at position 470 of the sequence and encodes a protein having an amino acid sequence of 792 amino acids, with a calculated molecular weight of 85.5 kDa. A Shine-Delgarno sequence (SD) is found at position 460. The HmbR receptor protein contains a signal peptidase I recognition sequence at residues 22 to 24 of the protein (underlined), consistent with the fact that it is an outer membrane protein.

A typical Fur binding nucleotide sequence (designated "Fur box") was found in the promoter region of the hmbR gene (FIGS. 2A-2H). Like hemin utilization in Yersiniae and Vibrio, heroin and hemoglobin utilization in Neisseria are known to be iron-inducible phenotypes (West and Sparling, 1985, Infect. Immun. 47: 388-394; Dyer et aI., 1987, Infect. Immun. 55: 2171-2175). In Gram-negative bacteria, conditional expression of many iron utilization genes is regulated by the Fur repressor, which recognizes a 19 bp imperfect dyad repeat (Fur-box) in the promoter regions of Fur-repressed genes. Recently, a genetic screen (FURTA) for the identification of Fur-regulated genes from different Gram-negative bacteria was described (Stojiljkovic et al., 1994, J. Mol. Biol. 236: 531-545), and this assay was used to test whether hmbR expression was controlled in this way. Briefly, a plasmid carrying a Fur-box sequence is transformed into an E. coli strain (H1717) which possesses a Fur-regulated lac fusion in the chromosome. Expression of this Fur-regulated lac fusion is normally repressed. Introduction of a multicopy Fur-box sequence on the plasmid titrates the available Fur repressor thus allowing expression of the Fur-regulated lac fusion (this phenotype is termed FURTA positive). Using this screen, the smallest insert fragment from cosmid plRS508 that produced a FURTA positive result was a 0.7 kb BamHI-NotI DNA fragment carried on plasmid pIRS528 (see FIG. 1). This result indicated that the 0.7 kb BamHI-NotI fragment carries a Fur-box and that gene expression from the hmbR promoter is controlled by a Fur-type operon.

The N. meningitidis hemoglobin receptor protein was expressed in vitro using an E. coli S30 extract system from Promega Biotech (Madison, Wis.). The 3.3 kb BamHI-HindIII fragment, expressed in vitro, encoded a 90 kDa protein which corresponds in size to the predicted molecular weight of the unprocessed HmbR receptor. SDS/10% PAGE analysis showing the observed M_(r) of 90K is shown in FIG. 3.

Immediately downstream of the hmbR gene (at positions 2955 to 3000 bp in FIG. 2) was found a short nucleotide sequence that is 99 % identical to the flanking sequence of the PIII gene of N. gonorrhoeae (Gotschlich et al., 1987, J. Exp. Med. 165: 471-482). The first 26 bp of this sequence represents one half of the inverted repeat (IR1) of the N. gonorrhoeae small repetitive element. This element is found in approximately 20 copies in both N. gonorrhoeae and N. meningitidis (Correia et al., 1988, J. Biol. Chem. 263: 12194-12198). The analysis of the nucleotide sequence from position 3027 to the ClaI (3984) restriction site (only the nucleotide sequence from BamHI (1) to HindIII (3370) is shown in FIGA. 2A-2H) indicated the presence of an IS1106 element (Knight et al., 1992, Mol. Microbiol. 6: 1565-1573). Interestingly, no nucleotide sequence similar to the ISl106 inverted repeat was found between the IR1 element and the beginning of the homology to IS1106.

These results were consistent with the cloning and identification of a novel hemoglobin receptor protein gene from N. meningitidis, embodied in a 3.3 kb BamHI/HindIII fragment of N. meningitidis genomic DNA.

EXAMPLE 5 Amino Acid Sequence Comparison of the N. meningitidis Hemoglobin Receptor Protein and Neisseria Lactoferrin and Transferrin Receptor Proteins

A comparison of the transferrin (Tbpl; Legrain et al., 1993, Gene 130: 81-90), lactoferrin (LbpA; Pettersson et al., 1993, Infect. Immun. 61: 4724-4733, and 1994, J. Bacteriol. 176: 1764-1766) and hemoglobin receptors (HmbR) from N. meningitidis is shown in FIGS. 4A-4C. The comparison was done with the CLASTAL program from the PC/GENE program package (Intelligenetics, Palo Alto, Calif.). Only the amino-terminal and carboxyl terminal segments of the proteins are shown. An asterisk indicates identity and a point indicates similarity at the amino acid level. Lactoferrin and transferrin receptors were found to share 44.4% identity in amino acid sequence. In contrast, homology between these proteins and the hemoglobin receptor disclosed herein was found to be significantly weaker (22% amino acid sequence identity with lactoferrin and 21% with transferrin receptor).

EXAMPLE 6 TonB/ExbBD-Dependence of Hemin Transport by the N. meningitidis Hemoglobin Receptor

It was known that the transport of iron-containing siderophores, some colicins and vitamin B12 across the outer membrane of E. coli depends on three cytoplasmic membrane proteins: TonB, ExbB and ExbD (Postle, 1990, Mol. Microbiol. 133: 891-898; Braun and Hantke, 1991, in Winkelmann, (ed.), Handbook of Microbial Iron Chelates, CRC Press, Boca Raton, Fla., pp. 107-138). In Yersinia and Hemophilus, heroin uptake was shown to be a TonB-dependent process (Stojiljkovic and Hantke, 1992, ibid.; Jarosik et al., 1994, Infect. Immun. 62: 2470-2477). Through direct interaction between the outer membrane receptors and the TonB cytoplasmic machinery, the substrate bound to the receptor is internalized into the periplasm (Heller et al., 1988, Gene 64: 147-153; Schoffler and Braun, 1989, Molec. Gen. Genet. 217: 378-383). This direct interaction has been associated with a particular amirto acid sequence in membrane proteins associated with the TonB machinery.

All TonB-dependent receptors in Gram-negative bacteria contain several regions of high homology in their primary structures (Lundrigan and Kadner, 1986, J. Biol. Chem. 261: 10797-10801). In the amino acid sequence comparison described in Example 5, putative TonB-boxes of all three proteins are underlined. The carboxyl terminal end of the HmbR receptor contains the highly conserved terminal phenylalanine and -11 arginine residues thought to be part of an outer membrane localization signal (Struyve et at., 1991, J. Mol. Biol. 218: 141-148; Koebnik, 1993, Trends Microbiol. 1: 201). At residue 6 of the mature HmbR protein, an amino acid sequence--ETTPVKA--is similar in sequence to the so called TonB-boxes of several Gram-negative receptors (Heller et al., 1988, ibid.). Interestingly, the putative TonB-box of HmbR has more homology to the TonB-box of the N. gonorrhoeae transferrin receptor (Cornelissen et al., 1992, J. Bacteriol. 174: 5788-5797) than to the TonB-boxes of E. coli siderophore receptors. When the sequence of the HmbR receptor was compared with other TonB-dependent receptors, the highest similarity was found with Y. enterocolitica HemR receptor although the similarity was not as high as to the Neisseria receptors.

In order to prove the TonB-dependent nature of the N. meningitidis hemoglobin receptor, hmbR was introduced into exbB and tonB mutants of E. coli EB53, and the ability of the strains to utilize hemin and hemoglobin as porphyrin and iron sources was assessed. In these assays, both mutants of E. coli EB53 were unable to use hemin either as a porphyrin source or as an iron source in the presence of a functional hmbR (Table II). The usage of hemoglobin as an iron source was also affected (Table II). These results are consistent with the notion that the hmbR gene product, the N. meningitidis hemoglobin receptor protein of the invention, is TonB-dependent, since expression of this gene in TonB wild type E. coli supported the use of hemin and hemoglobin as sole iron source in the experiments disclosed in Example 2.

EXAMPLE 7 Functional Demonstration that the hmbR Gene Product is the Hemoglobin Receptor Protein in N. meningitidis

As shown in the data presented in Table II, hmbR mediated both heroin and hemoglobin utilization when expressed in E. coli, but hemoglobin utilization was less vigorous than hemin utilization. To determine if the HmbR receptor has the same specificity in N. meningitidis, hmbR was inactivated with a 1.2 kb kanamycin cassette (aphA-3; Nassif et al., 1991, ibid.) and transformed into wild-type N. meningitidis 8013 clone 6 cells. The inactivation of the chromosomal hmbR copy of the Km-resistant transformants was confirmed by Southern hybridization, as shown in FIG. 5. As can be seen from FIG. 5, wild-type N. meningitidis genomic DNA contains only one copy of the hmbR gene (lanes 1 and 3). In the Km^(r) transformants, the size of the DNA fragments containing the wild-type gene has increased by 1.2 kb, which is the size of the Kan cassette (FIG. 5, lanes 2 and 4). When tested for its ability to utilize different iron-containing compounds, these mutant cells were found to be unable to use hemoglobin-bound iron, regardless of the source (human, bovine, baboon, mouse). The ability of the mutant to utilize hemoglobin-haptoglobin was not tested because the wild-type N. meningitidis strain is unable to use haptoglobin-haemoglobin complex as an iron source. However, the mutant was still able to use heroin iron, lactoferrin- and transferrin-bound iron as well as titrate-iron (Table II). As the iron-containing component of hemoglobin is hemin, a hemoglobin receptor would be expected to be capable of transporting hemin into the periplasm. Indeed, the cloning strategy disclosed herein depended on the ability of the cloned meningococcal receptor to transport hemin into the periplasm of E. coli. These results strongly suggest that N. meningitidis has at least two functional receptors that are involved in the internalization of hemin-containing compounds. One is the hemoglobin receptor described herein, which allows the utilization of both hemin and hemoglobin as iron sources. The other putative receptor in N. meningitidis is a hemin receptor which allows utilization of only heroin. This schema is also consistent with the isolation of several cosmid clones that allow E. coli EB53 to utilize hemin. DNAs from these cosmids do not hybridize with the hmbR probe, indicating that these clones encode a structurally-distinct receptor protein capable of transporting hemin into the periplasm of N. meningitidis cells.

EXAMPLE 8 Attenuation of Virulence in hmbR Mutant N. meningitidis Cells In Vivo

In order to test the importance of hemoglobin and hemin scavenging systems of N. meningitidis in vivo, the hmbR -mutant and the wild type strain were inoculated into 5 day old infant rats and the numbers of bacteria recovered from blood and cerebrospinal fluid were followed. In these experiments, the method for the assessing N. meningitidis virulence potential was essentially the same as described by Nassif et aI. (1992, ibid.) using infant inbred Lewis rats (Charles River, Saint Aubin les Elbeufs, France). Inbred rats were used to minimize individual variations. Briefly, the 8013 strain was reactivated by 3 animal passages. After the third passage, bacteria were kept frozen in aliquots at -80° C. To avoid the possibility that modifications in the course of infection could result from selection of one spontaneous avirulent variant, one aliquot from the animal-passed frozen stock of 8013 was transformed with chromosomal DNA from the hmbR mutant, the resultant Kan^(r) transformants were pooled without further purification and kept frozen at -80° C. For each experiment, all infant rats were from the same litter. N. meningitidis 8013 was grown overnight and 2×10⁶ bacteria injected intraperitoneally into the infant rat. Three rats were used for each meningococcal strain. The course of infection was followed over a 24 hours time period with blood collected at the indicated times. At the 24 h time period, the rats were sacrificed, the cerebrospinal fluid (CSF) collected and the number of colony-forming units (CFU) determined. Each experiment was performed in replicate; similar results were obtained both times.

The results of these experiments are shown in FIG. 6. The hmbR⁻ strain, which is unable to use hemoglobin as an iron source, was recovered from the blood of infected animals in significantly lower numbers when compared with the wild type strain. Both the mutant and the wild type strain were still able to cross the blood-brain barrier as indicated by the isolation of bacteria from the cerebrospinal fluid. These results indicate that hemoglobin represents an important iron source for N. meningitidis during growth in vivo.

It should be understood that the foregoing disclosure emphasizes certain specific embodiments of the invention and that all modifications or alternatives equivalent thereto are within the spirit and scope of the invention as set forth in the appended claims.

    __________________________________________________________________________     SEQUENCE LISTING                                                               (1) GENERAL INFORMATION:                                                       (iii) NUMBER OF SEQUENCES: 2                                                   (2) INFORMATION FOR SEQ ID NO:1:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 3318 base pairs                                                    (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: DNA (genomic)                                              (ix) FEATURE:                                                                  (A) NAME/KEY: CDS                                                              (B) LOCATION: 470..2848                                                        (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                        AGAACTAGTGGATCCAATTTGGGCGCGGCGTTTTTGTTCAAACACGCCCAAAAACTCGAT60                 TACAACGGCGAACACGGCGCGCGCCACCTCGCTCCGCATCCCGACGGGCCGCGGCAAACA120                CTGGCGCGCCTTCGTCGAGCATCTGAACGCTTTGAACCTGACTCCCGAAGCCGAAGCGGA180                AGCCATTCAAGGCGCGCGCGAAGCCTTTGCATTCTACAAAGTCGTGTTGCGCGAAACCTT240                CGGCTTGGCAGCCGATGCCGAAGCCCCCGAAGGTATGATGCCGCACAGGCACTAAAAAAT300                AATCGAACCAAATAAACAAGGTCTCGGCATAGCTGTTTGCAGGGACCTTTAATTACACGG360                CGCGGCTTTGTTTACATGGATTACTGTCTTATTAAATATTAATGATTATCATAAAATCTA420                TTATTCGCTAACCGATGGATGAACAATCCATACATCTTGAGTTGATAATATGAAA475                     MetLys                                                                         CCATTACAAATGCTCCCTATCGCCGCGCTGGTCGGCAGTATTTTCGGC523                            ProLeuGlnMetLeuProIleAlaAlaLeuValGlySerIlePheGly                               51015                                                                          AATCCGGTCTTTGCGGCAGATGAAGCTGCAACTGAAACCACACCCGTT571                            AsnProValPheAlaAlaAspGluAlaAlaThrGluThrThrProVal                               202530                                                                         AAGGCAGAGGTAAAAGCAGTGCGCGTTAAAGGCCAGCGCAATGCGCCT619                            LysAlaGluValLysAlaValArgValLysGlyGlnArgAsnAlaPro                               35404550                                                                       GCGGCTGTGGAACGCGTCAACCTTAACCGTATCAAACAAGAAATGATA667                            AlaAlaValGluArgValAsnLeuAsnArgIleLysGlnGluMetIle                               556065                                                                         CGCGACAACAAAGACTTGGTGCGCTATTCCACCGATGTCGGCTTGAGC715                            ArgAspAsnLysAspLeuValArgTyrSerThrAspValGlyLeuSer                               707580                                                                         GACAGCGGCCGCCATCAAAAAGGCTTTGCTGTTCGCGGCGTGGAAGGC763                            AspSerGlyArgHisGlnLysGlyPheAlaValArgGlyValGluGly                               859095                                                                         AACCGTGTCGGCGTGAGCATAGACGGCGTAAACCTGCCTGATTCCGAA811                            AsnArgValGlyValSerIleAspGlyValAsnLeuProAspSerGlu                               100105110                                                                      GAAAACTCGCTGTACGCCCGTTATGGCAACTTCAACAGCTCGCGTCTG859                            GluAsnSerLeuTyrAlaArgTyrGlyAsnPheAsnSerSerArgLeu                               115120125130                                                                   TCTATCGACCCCGAACTCGTGCGCAACATCGACATCGTAAAAGGGGCG907                            SerIleAspProGluLeuValArgAsnIleAspIleValLysGlyAla                               135140145                                                                      GACTCTTTCAATACCGGCAGCGGCGCCTTGGGCGGCGGTGTGAATTAC955                            AspSerPheAsnThrGlySerGlyAlaLeuGlyGlyGlyValAsnTyr                               150155160                                                                      CAAACCCTGCAAGGACGTGACTTACTGTTGCCTGAACGGCAGTTCGGC1003                           GlnThrLeuGlnGlyArgAspLeuLeuLeuProGluArgGlnPheGly                               165170175                                                                      GTGATGATGAAAAACGGTTACAGCACGCGTAACCGTGAATGGACAAAT1051                           ValMetMetLysAsnGlyTyrSerThrArgAsnArgGluTrpThrAsn                               180185190                                                                      ACCCTCGGTTTCGGCGTGAGCAACGACCGCGTGGATGCCGCTTTGCTG1099                           ThrLeuGlyPheGlyValSerAsnAspArgValAspAlaAlaLeuLeu                               195200205210                                                                   TATTCGCAACGGCGCGGCCATGAAACTGAAAGCGCGGGCAAGCGTGGT1147                           TyrSerGlnArgArgGlyHisGluThrGluSerAlaGlyLysArgGly                               215220225                                                                      TATCCGGTAGAGGGTGCTGGTAGCGGAGCGAATATCCGTGGTTCTGCG1195                           TyrProValGluGlyAlaGlySerGlyAlaAsnIleArgGlySerAla                               230235240                                                                      CGCGGTATTCCTGATCCGTCCCAACACAAATACCACAGCTTCTTGGGT1243                           ArgGlyIleProAspProSerGlnHisLysTyrHisSerPheLeuGly                               245250255                                                                      AAGATTGCTTATCAAATCAACGACAACCACCGCATCGGCGCATCGCTC1291                           LysIleAlaTyrGlnIleAsnAspAsnHisArgIleGlyAlaSerLeu                               260265270                                                                      AACGGTCAGCAGGGGCATAATTACACGGTTGAAGAGTCTTACAACCTG1339                           AsnGlyGlnGlnGlyHisAsnTyrThrValGluGluSerTyrAsnLeu                               275280285290                                                                   CTTGCTTCTTATTGGCGTGAAGCTGACGATGTCAACAGACGGCGTAAC1387                           LeuAlaSerTyrTrpArgGluAlaAspAspValAsnArgArgArgAsn                               295300305                                                                      ACCAACCTCTTTTACGAATGGACGCCGGAATCCGACCGGTTGTCTATG1435                           ThrAsnLeuPheTyrGluTrpThrProGluSerAspArgLeuSerMet                               310315320                                                                      GTAAAAGCGGATGTCGATTATCAAAAAACCAAAGTATCTGCGGTCAAC1483                           ValLysAlaAspValAspTyrGlnLysThrLysValSerAlaValAsn                               325330335                                                                      TACAAAGGTTCGTTCCCGATAGAGGATTCTTCCACCTTGACACGTAAC1531                           TyrLysGlySerPheProIleGluAspSerSerThrLeuThrArgAsn                               340345350                                                                      TACAATCAAAAGGACTTGGATGAAATCTACAACCGCAGTATGGATACC1579                           TyrAsnGlnLysAspLeuAspGluIleTyrAsnArgSerMetAspThr                               355360365370                                                                   CGCTTCAAACGCATTACCCTGCGTTTGGACAGCCATCCGTTGCAACTC1627                           ArgPheLysArgIleThrLeuArgLeuAspSerHisProLeuGlnLeu                               375380385                                                                      GGGGGGGGGCGACACCGCCTGTCGTTTAAAACTTTCGCCAGCCGCCGT1675                           GlyGlyGlyArgHisArgLeuSerPheLysThrPheAlaSerArgArg                               390395400                                                                      GATTTTGAAAACCTAAACCGCGACGATTATTACTTCAGCGGCCGTGTT1723                           AspPheGluAsnLeuAsnArgAspAspTyrTyrPheSerGlyArgVal                               405410415                                                                      GTTCGAACCACCAGCAGTATCCAGCATCCGGTGAAAACCACCAACTAC1771                           ValArgThrThrSerSerIleGlnHisProValLysThrThrAsnTyr                               420425430                                                                      GGTTTCTCACTGTCTGACCAAATTCAATGGAACGACGTGTTCAGTAGC1819                           GlyPheSerLeuSerAspGlnIleGlnTrpAsnAspValPheSerSer                               435440445450                                                                   CGCGCAGGTATCCGTTACGATCATACCAAAATGACGCCTCAGGAATTG1867                           ArgAlaGlyIleArgTyrAspHisThrLysMetThrProGlnGluLeu                               455460465                                                                      AATGCCGAGTGTCATGCTTGTGACAAAACACCGCCTGCAGCCAACACT1915                           AsnAlaGluCysHisAlaCysAspLysThrProProAlaAlaAsnThr                               470475480                                                                      TATAAAGGCTGGAGCGGTTTTGTCGGCTTGGCGGCGCAACTGAATCAG1963                           TyrLysGlyTrpSerGlyPheValGlyLeuAlaAlaGlnLeuAsnGln                               485490495                                                                      GCTTGGCGTGTCGGTTACGACATTACTTCCGGCTACCGTGTCCCCAAT2011                           AlaTrpArgValGlyTyrAspIleThrSerGlyTyrArgValProAsn                               500505510                                                                      GCGTCCGAAGTGTATTTCACTTACAACCACGGTTCGGGTAATTGGCTG2059                           AlaSerGluValTyrPheThrTyrAsnHisGlySerGlyAsnTrpLeu                               515520525530                                                                   CCCAATCCCAACCTGAAAGCCGAGCGCACGACCACCCACACCCTCTCT2107                           ProAsnProAsnLeuLysAlaGluArgThrThrThrHisThrLeuSer                               535540545                                                                      CTGCAAGGCCGCAGCGAAAAAGGTACTTTGGATGCCAACCTGTATCAA2155                           LeuGlnGlyArgSerGluLysGlyThrLeuAspAlaAsnLeuTyrGln                               550555560                                                                      AGCAATTACCGCAATTTCCTGTCTGAAGAGCAGAAGCTGACCACCAGC2203                           SerAsnTyrArgAsnPheLeuSerGluGluGlnLysLeuThrThrSer                               565570575                                                                      GGCGATGTCAGCTGTACTCAGATGAATTACTACTACGGTATGTGTAGC2251                           GlyAspValSerCysThrGlnMetAsnTyrTyrTyrGlyMetCysSer                               580585590                                                                      AATCCTTATTCCGAAAAACTGGAATGGCAGATGCAAAATATCGACAAG2299                           AsnProTyrSerGluLysLeuGluTrpGlnMetGlnAsnIleAspLys                               595600605610                                                                   GCCAGAATCCGCGGTATCGAGCTGACGGGCCGTCTGAATGTGGACAAA2347                           AlaArgIleArgGlyIleGluLeuThrGlyArgLeuAsnValAspLys                               615620625                                                                      GTAGCGTCTTTTGTTCCTGAGGGCTGGAAACTGTTCGGCTCGCTGGGT2395                           ValAlaSerPheValProGluGlyTrpLysLeuPheGlySerLeuGly                               630635640                                                                      TATGCGAAAAGCAAACTGTCGGGCGACAACAGCCTGCTGTCCACCCAG2443                           TyrAlaLysSerLysLeuSerGlyAspAsnSerLeuLeuSerThrGln                               645650655                                                                      CCGTTGAAAGTGATTGCCGGTATCGACTATGAAAGTCCGAGCGAAAAA2491                           ProLeuLysValIleAlaGlyIleAspTyrGluSerProSerGluLys                               660665670                                                                      TGGGGCGTGTTCTCCCGCCTGACCTATCTGGGCGCGAAAAAGGTCAAA2539                           TrpGlyValPheSerArgLeuThrTyrLeuGlyAlaLysLysValLys                               675680685690                                                                   GACGCGCAATACACCGTTTATGAAAACAAGGGCTGGGGTACGCCTTTG2587                           AspAlaGlnTyrThrValTyrGluAsnLysGlyTrpGlyThrProLeu                               695700705                                                                      CAGAAAAAGGTAAAAGATTACCCGTGGCTGAACAAGTCGGCTTATGTG2635                           GlnLysLysValLysAspTyrProTrpLeuAsnLysSerAlaTyrVal                               710715720                                                                      TTCGATATGTACGGCTTCTACAAACCGGTGAAAAACCTGACTTTGCGT2683                           PheAspMetTyrGlyPheTyrLysProValLysAsnLeuThrLeuArg                               725730735                                                                      GCAGGCGTATATAATGTGTTCAACCGCAAATACACCACTTGGGATTCC2731                           AlaGlyValTyrAsnValPheAsnArgLysTyrThrThrTrpAspSer                               740745750                                                                      CTGCGCGGCCTGTATAGCTACAGCACCACCAACTCGGTCGACCGCGAT2779                           LeuArgGlyLeuTyrSerTyrSerThrThrAsnSerValAspArgAsp                               755760765770                                                                   GGCAAAGGCTTAGACCGCTACCGCGCCCCAAGCCGTAATTACGCCGTA2827                           GlyLysGlyLeuAspArgTyrArgAlaProSerArgAsnTyrAlaVal                               775780785                                                                      TCGCTGGAATGGAAGTTTTAATCTGGTATTATTGAATTAATCGCCTTG2875                           SerLeuGluTrpLysPhe                                                             790                                                                            TTGAAAATTAAAGCCGTCCGAATTGTGTTCAAGAACTCATTCGGACGGTTTTTACCGAAT2935               CTGTGTGTGGGTTTATAGTGGATTAACAAAAATCAGGACAAGGCGACGAAGCCGCAGACA2995               GTACAGATAGTACGGAACCGATTCACTTGGTGAGACCTTTGCAAAATTCCTTTCCCTCCC3055               GACAGCCGAAACCCAAACACAGGTTTTCGGCTGTTTTCGCCCCAAATACCTCCTAATTCT3115               ACCCAAATACCCCCTTAATCCTCCCCGATACCCGATAATCAGGCATCCGGCGCCTTTAGG3175               CGGCAGCGGGCGCACTTAACCTGTTGGCGGCTTTCAAAAGGTTCAAACACATCGCCTTCA3235               GGTGGCTTTGCGCACTCACTTTAATCAGTCCGAAATAGGCCGCCCGCGCATAGCAGAACT3295               TACGGTGCAGCGTACCGAACTTT3318                                                    (2) INFORMATION FOR SEQ ID NO:2:                                               (i) SEQUENCE CHARACTERISTICS:                                                  (A) LENGTH: 792 amino acids                                                    (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                           (ii) MOLECULE TYPE: protein                                                    (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                        MetLysProLeuGlnMetLeuProIleAlaAlaLeuValGlySerIle                               151015                                                                         PheGlyAsnProValPheAlaAlaAspGluAlaAlaThrGluThrThr                               202530                                                                         ProValLysAlaGluValLysAlaValArgValLysGlyGlnArgAsn                               354045                                                                         AlaProAlaAlaValGluArgValAsnLeuAsnArgIleLysGlnGlu                               505560                                                                         MetIleArgAspAsnLysAspLeuValArgTyrSerThrAspValGly                               65707580                                                                       LeuSerAspSerGlyArgHisGlnLysGlyPheAlaValArgGlyVal                               859095                                                                         GluGlyAsnArgValGlyValSerIleAspGlyValAsnLeuProAsp                               100105110                                                                      SerGluGluAsnSerLeuTyrAlaArgTyrGlyAsnPheAsnSerSer                               115120125                                                                      ArgLeuSerIleAspProGluLeuValArgAsnIleAspIleValLys                               130135140                                                                      GlyAlaAspSerPheAsnThrGlySerGlyAlaLeuGlyGlyGlyVal                               145150155160                                                                   AsnTyrGlnThrLeuGlnGlyArgAspLeuLeuLeuProGluArgGln                               165170175                                                                      PheGlyValMetMetLysAsnGlyTyrSerThrArgAsnArgGluTrp                               180185190                                                                      ThrAsnThrLeuGlyPheGlyValSerAsnAspArgValAspAlaAla                               195200205                                                                      LeuLeuTyrSerGlnArgArgGlyHisGluThrGluSerAlaGlyLys                               210215220                                                                      ArgGlyTyrProValGluGlyAlaGlySerGlyAlaAsnIleArgGly                               225230235240                                                                   SerAlaArgGlyIleProAspProSerGlnHisLysTyrHisSerPhe                               245250255                                                                      LeuGlyLysIleAlaTyrGlnIleAsnAspAsnHisArgIleGlyAla                               260265270                                                                      SerLeuAsnGlyGlnGlnGlyHisAsnTyrThrValGluGluSerTyr                               275280285                                                                      AsnLeuLeuAlaSerTyrTrpArgGluAlaAspAspValAsnArgArg                               290295300                                                                      ArgAsnThrAsnLeuPheTyrGluTrpThrProGluSerAspArgLeu                               305310315320                                                                   SerMetValLysAlaAspValAspTyrGlnLysThrLysValSerAla                               325330335                                                                      ValAsnTyrLysGlySerPheProIleGluAspSerSerThrLeuThr                               340345350                                                                      ArgAsnTyrAsnGlnLysAspLeuAspGluIleTyrAsnArgSerMet                               355360365                                                                      AspThrArgPheLysArgIleThrLeuArgLeuAspSerHisProLeu                               370375380                                                                      GlnLeuGlyGlyGlyArgHisArgLeuSerPheLysThrPheAlaSer                               385390395400                                                                   ArgArgAspPheGluAsnLeuAsnArgAspAspTyrTyrPheSerGly                               405410415                                                                      ArgValValArgThrThrSerSerIleGlnHisProValLysThrThr                               420425430                                                                      AsnTyrGlyPheSerLeuSerAspGlnIleGlnTrpAsnAspValPhe                               435440445                                                                      SerSerArgAlaGlyIleArgTyrAspHisThrLysMetThrProGln                               450455460                                                                      GluLeuAsnAlaGluCysHisAlaCysAspLysThrProProAlaAla                               465470475480                                                                   AsnThrTyrLysGlyTrpSerGlyPheValGlyLeuAlaAlaGlnLeu                               485490495                                                                      AsnGlnAlaTrpArgValGlyTyrAspIleThrSerGlyTyrArgVal                               500505510                                                                      ProAsnAlaSerGluValTyrPheThrTyrAsnHisGlySerGlyAsn                               515520525                                                                      TrpLeuProAsnProAsnLeuLysAlaGluArgThrThrThrHisThr                               530535540                                                                      LeuSerLeuGlnGlyArgSerGluLysGlyThrLeuAspAlaAsnLeu                               545550555560                                                                   TyrGlnSerAsnTyrArgAsnPheLeuSerGluGluGlnLysLeuThr                               565570575                                                                      ThrSerGlyAspValSerCysThrGlnMetAsnTyrTyrTyrGlyMet                               580585590                                                                      CysSerAsnProTyrSerGluLysLeuGluTrpGlnMetGlnAsnIle                               595600605                                                                      AspLysAlaArgIleArgGlyIleGluLeuThrGlyArgLeuAsnVal                               610615620                                                                      AspLysValAlaSerPheValProGluGlyTrpLysLeuPheGlySer                               625630635640                                                                   LeuGlyTyrAlaLysSerLysLeuSerGlyAspAsnSerLeuLeuSer                               645650655                                                                      ThrGlnProLeuLysValIleAlaGlyIleAspTyrGluSerProSer                               660665670                                                                      GluLysTrpGlyValPheSerArgLeuThrTyrLeuGlyAlaLysLys                               675680685                                                                      ValLysAspAlaGlnTyrThrValTyrGluAsnLysGlyTrpGlyThr                               690695700                                                                      ProLeuGlnLysLysValLysAspTyrProTrpLeuAsnLysSerAla                               705710715720                                                                   TyrValPheAspMetTyrGlyPheTyrLysProValLysAsnLeuThr                               725730735                                                                      LeuArgAlaGlyValTyrAsnValPheAsnArgLysTyrThrThrTrp                               740745750                                                                      AspSerLeuArgGlyLeuTyrSerTyrSerThrThrAsnSerValAsp                               755760765                                                                      ArgAspGlyLysGlyLeuAspArgTyrArgAlaProSerArgAsnTyr                               770775780                                                                      AlaValSerLeuGluTrpLysPhe                                                       785790                                                                         __________________________________________________________________________ 

What we claim is:
 1. An isolated and purified recombinant nucleic acid encoding a hemoglobin receptor protein from a Neisseria species, wherein the nucleic acid encodes a hemoglobin receptor protein having an amino acid sequence that is the amino acid sequence depicted as Seq. I.D. No.
 2. 2. A recombinant expression construct comprising a nucleic acid that encodes a hemoglobin receptor protein from a Neisseria species, wherein the nucleic acid encodes a hemoglobin receptor protein having an amino acid sequence that is the amino acid sequence depicted as Seq. I.D. No.
 2. 3. A transformed cell comprising the recombinant expression construct of claim
 2. 